A little-known Green candidate is challenging Russel Norman for co-leadership of the party.

Auckland Council policy analyst David Hay, 52, says Norman has done a great job but after six years it's time for a change.

Hay is ranked number 16 on the party's list and stood in Epsom at the last election, and in Rodney in 2008. He says there is "fresh talent" among the membership.

In a statement, he said: "There is a real possibility that the Greens will be in government after the next election, and the party needs to be putting its 'A' team forward."

Hay says he will build the party's presence in Auckland, lift its performance and focus on environmental and economic sustainability, which is currently diluted by parliamentary issues.

"I want to put Russel's leadership to the test: if he wins out, then he will lead the party into government with a renewed mandate. If somebody else does, then the party will be even stronger going into the next election," he said.

Three of the 14 MPs are based in Auckland.

"We currently lack sufficient presence here, in New Zealand's largest city, where a third of the population live."

The leadership will be voted on in June at an annual conference. Norman assumed co-leadership in 2006, Metiria Turei followed in 2009.

Norman said he hadn't been challenged since 2006, but is "very confident" he will be re-elected.

Asked about Hay's views, he said "it's an open democratic process, he's entitled to his opinion."